The biological characteristics of dicarboximide‐resistant isolates of Monilinia fructicola from New Zealand stone‐fruit orchards

Abstract

Dicarboximide‐resistant isolates of Monilinia fructicola were detected in New Zealand stone fruit orchards in 1985. The EC50 values of resistant isolates ranged from 3 to 217 mg a.i./l iprodione, compared with 0‐3 to 0‐7 mg a.i./l for sensitive isolates. The degree of dicarboximide resistance was maintained over nine generations in fruit tissues in most isolates, but in four isolates there was a significant decline. Three resistant and two sensitive isolates were selected for further study on agar and host tissues. Resistant isolates caused disease, grew and sporulated as well as sensitive isolates on flowers not amended with dicarboximide fungicides, but some were less fit on fruit. The pathogenicity and spore production of a resistant strain on flowers was reduced significantly by dicarboximide applied prior to pathogen inoculation. Fitness of isolates on flowers and on fruit was poorly correlated. Resistant isolates were significantly less competitive than sensitive isolates when mixed inocula were applied to flowers and fruit. The relative performance on flowers and fruit was not a reliable indicator of competitive ability.

Sensitivity of Monilinia fructicola from Spanish peach orchards to thiophanate-methyl, iprodione, and cyproconazole: fitness analysis and competitiveness

“…This high EC 50 is in agreement with the high EC 50 's that have been reported for the growth response curves of other high fungicideresistant M. fructicola populations (Ma et al 2003;Yoshimura et al 2004). The EC 5 0 's (2.17-2.45 μg ml −1 ) of the growth response curve of the Iresistant isolates were slightly lower than those that have been reported in another I-resistant M. fructicola population in New Zealand (>3 μg ml −1 ) by Elmer and Gaunt (Elmer and Gaunt 1994). The EC 50 's (0.0095-0.1162 μg ml −1 ) of the growth response curve of the CPZ-sensitive isolates were consistent with those that have been reported for CPZ-sensitive M. fructicola populations from New York (Wilcox and Burr 1994), South Carolina, and Georgia in the USA (Holb and Schnabel 2007;Schnabel et al 2004;Villani and Cox 2011); but something differences with that reported by Lichtemberg in Brazil (Lichtemberg et al 2014).…”

“…Iprodione (I) is a DCF, and has been used for controlling brown rot for almost two decades in the USA and resistance has not yet been reported in field M. fructicola isolates (Ma et al 2006;Yoshimura et al 2004). However, reduced I sensitivity has been reported in M. fructicola isolates in New Zealand (Elmer and Gaunt 1994) and in Australia (Wherrett et al 2001). Cyproconazole (CPZ) is a DMI-fungicide that acts inhibiting sterol biosynthesis in membranes, and it is considered by FRAC as a medium risk one (Fishel and Dewdney 2006), DMI-resistance has been already reported in M. fructicola populations from the USA, (Luo and Schnabel 2008;Schnabel et al 2004;Villani and Cox 2011;Chen et al 2013) andin Brazil (May-De Mio et al 2011).…”

“…MBC-resistant M. fructicola isolates have been found in countries where the fungus has been long established, such as the USA (Ma et al 2003;Michailides et al 1987;Zhu et al 2010), Australia (Penrose 1990), New Zealand (Elmer and Gaunt 1994;Sanoamuang and Gaunt 1995) and Brazil (May-de Mio et al 2011). The mechanism of MBC action (including thiophanate-methyl (TM)) is to disrupt mitosis and cell division, and the Fungicide Resistance Action Committee (FRAC) has classified the TM as a fungicide class at high risk to develop resistance (Fishel and Dewdney 2006).…”

Involvement of phenolic compounds in host resistance againstBotrytis cinereainleaves of the two commercially important kiwifruit (Actinidia chinensisandA. deliciosa) cultivars

“…Laboratory trials were carried out at 18°C, by placing excised leaves on wire racks in 21-litre airtight plastic bins, with the leaf petioles suspended in a sterile solution of 20 ml/litre and ethanol and 20 g/litre sucrose in distilled water (Elmer 1990). Under these conditions, leaves could be maintained for 8-12 days without exhibiting signs of physiological stress, and during this time wounding, inoculation, and disease assessments were performed, followed by extraction and measurement of phenolic compounds.…”

Peach Brown Rot: Still in Search of an Ideal Management Option

“…In addition, the contamination of the environment should be avoided [138]. Finally, the steady rise in the development and occurrence of Monilinia strains resistant to CF, worldwide, has been reported [133,134,[138][139][140]. With all these adverse implications it is, therefore, pertinent to search for alternatives control strategies as IPM with lasting effect, enhancing consumer acceptability, and at the same time environmentally friendly.…”